Improvement to LiDAR data labeling

[brunofavs]

It would be useful if the user could know how many total points are selected and how many are currently selected by the Selected Points Publisher.

For example, in this collection :

I accidentally forgot to deselect the points in the very last line, and it caused my calibration to fail completely.

It would be helpful if the user could just select my entire pattern and see "oh my pattern selection has x points but the total selected points is x+100". This way the user would immediately know if he messed up the labeling.

Another possibly more elaborate way would be to integrate any pcd outlier algorithm to remove those points maybe

[brunofavs]

Or a way to hide the unselected points could work as well